The legally-required dosage tests for diagnostic and therapeutic radiopharmaceuticals are conducted directly at LNHB. However, novel solutions must be found for new compounds with very short half-lives. Some of these compounds—like 15O—must be used within five minutes after they are manufactured, making it impossible to send them to the lab for testing. List has developed a miniature measurement instrument to test these radiopharmaceuticals right where they will be used, at the hospital.

The instrument—a liquid scintillation counter made up of three commercially-available miniature photomultiplier tubes—provides a primary measurement of a sample's activity. The detection yield is arrived at deductively from the probability that the photons emitted by disintegration will be detected by two (or three) of the tubes simultaneously. This method is usually used by national radioactivity metrology labs but with non-transportable equipment.

The potential applications for the miniature counter reach beyond testing therapeutic compounds. It could be used to compare primary standards across borders for substances that cannot be shipped internationally for safety reasons. And, more broadly, the method can be used for any situation in which an on-site measurement is required.